It is often desirable and frequently absolutely necessary to sample or test a portion of tissue from humans and even animals to aid in the diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions and other diseases or disorders. Typically in the case of cancer or the suspicion of malignant tumors, a very important process called tissue biopsy is performed to establish whether cells are cancerous.
Biopsy may be done by an open or closed technique. Open biopsy removes the entire tissue mass or a part of the tissue mass. Closed biopsy on the other hand is usually performed with a needle-like instrument and may be either an aspiration (hollow needle on a syringe) or a core biopsy (special tissue cutting needle design). In needle aspiration biopsy, individual cells or clusters of cells are obtained for cytologic examination. In core biopsy, a segment of tissue is obtained for histologic examination which may be done as a frozen section or paraffin section.
The methods and procedures of obtaining tissue samples for cytologic or histologic examination have been performed historically by manual insertion and manipulation of the needle. These procedures are performed "blind" by the physician and guided by "feel" and known anatomic "landmarks".
Tumors are first noted in a patient by one of three ways, palpation, x-ray imaging or ultrasound imaging. Once a tumor is identified, a biopsy procedure is performed. Modern medical opinion dictates early detection of cancer, which increases the likelihood of successful treatment. Biopsy are performed on "Tumor Masses" as small as 2 millimeters in diameter. This procedure is performed under ultrasound or x-ray guidance. Tumors of this size cannot be biopsied reliably by hand since the tumor is about the same size as the biopsy needle. Manual attempts at biopsy can push the tumor away without piercing the mass. Automatic puncture devices are needed to accelerate the needle at such a velocity that even a small tumor can be pierced.
Two very important innovations in the field of medical technology have influenced the field of tissue biopsy in the last five years.
One, the use of tissue imaging devices which allow the physician to "see" inside the body and visually guide the needle to the tumor mass.
Two, the invention of the Automatic Core Biopsy Device (ACBD) or "Biopsy Gun". The ACBD is an instrument which propels a needle set with considerable force and speed to pierce the tumor mass and collect the tissue sample. This ACBD device has allowed physicians to test tissue masses in the early stages of growth and has contributed to the medical trend of early diagnosis and successful treatment of cancer.
Examples of such ACBD devices have been described with respect to the collection of tissue samples in U.S. Pat. Nos. 4,651,752, 4,702,260, and 4,243,048.
Historically, Automated Core Biopsy Devices (ACBD) have used the "Tru-Cut" needle set design. The "Tru-Cut" needle is comprised of an inner notched stylet with an outer cannula. The stylet is advanced into the tissue under spring power followed by the cannula which cuts and traps the tissue sample in the notch of the stylet. The "Tru-Cut" needle yields a core sample which is semi-circular in cross section, with length of the core sample determined by the stroke of the ACBD.
The stylet is a needle with a notched cut out at the distal end. The cannula is a hollow needle with an angled cutting surface at the distal end which slides over the stylet. When the stylet is pushed into tissue, the tissue is pierced and relaxes into the notched cut out. When the cannula is slid forward, the tissue in the notch of the stylet is sliced off and retained in the notch until the cannula is drawn back.
Subsequent improvements to the "Tru-Cut" needle design have been introduced and are described in U.S. Pat. No. 5,449,001.
In certain biopsy procedures where the suspect mass is in close proximity to main arteries or where potential damage could occur from the rapid automated advance of the stylet on the ACBD, it is often desirable for the physician to manually place the inner stylet of the needle set into the biopsy area and cut the prolapsed tissue with the advancement of the cannula. This process is commonly referred to as closed "semi-automated" biopsy, due to the fact that the stylet is manually deployed and the cannula is automatically advanced under spring power.
There are numerous prior art devices on the market that employ this semi-automated process. However, in prior art designs, if the physician requires a biopsy device which cycles the needle set a short or longer distance into the tissue mass, a separate device for each needle distance desired has to be purchased. Current prior art devices have captive needle sets which require the physician to have many different styles of devices available to perform the range of procedures that are encountered in a biopsy procedure. These prior art devices are typically a small disposable plastic frame that houses a spring to power the cannula and a push rod to manually deploy the stylet. The stylet and cannula are integral to the plastic frame and cannot be removed. These prior art devices are supplied with a specific needle gauge, needle length and predetermined extension of the stylet for each individual device. This is a design limitation because it creates a situation of compromise between the physician's desire to use the optimum needle for a given procedure and the need to overstock all the possible combinations of needle gauges, lengths and predetermined extensions of the stylet that are available for a biopsy procedure. Furthermore, in the era of managed health care, the cost of biopsy procedures has come under scrutiny. The disposable single use devices are expensive and not desirable due to their high single use cost.
Accordingly, each biopsy procedure, given the anatomic location of the biopsy area and tissue density, requires a particular needle gauge, a specific needle length and a predetermined extension of the stylet into the tissue to obtain the optimum biopsy sample for that particular procedure. Thus, prior art designs of the ACBD have a need for a design that allows the interchangeability of the needle sets to accommodate the parameters of the biopsy procedure to be performed.
On the other hand, the physician may use a prior art device that is capable of functioning at different distance settings to perform a range of biopsy procedures. However, such an adjustable device is mechanically complicated and requires external settings to be made to allow the mechanism to perform at different needle advancement distances. Also the reusable handles have, in prior art, been costly to obtain because of the expense of manufacturing a complicated mechanical design. Since the mechanism of the prior art ACBD is designed to have a stylet that moves forward first and then activates the cannula, thus advancing the needles in their proper sequence, these prior art devices require many high tolerance mechanical moving parts with precision bushings in order to have the device operate properly. The required repeated use of the reusable design dictates that the mechanical design be robust and operates many cycles without undue wear or failure. These requirements have produced in prior art, ACBDs that are heavy, large and costly due to their complicated mechanical designs.
Thus, the size, weight and expense of single use and reusable prior art ACBD's have limited their use. An improved design is needed that gives the physician a small, light weight, easy to operate and cost effective design that improves the function of obtaining a tissue sample of a predetermined size.